1. Field of the Invention
The present invention relates to a lip type seal corresponding to one kind of a sealing apparatus. The lip type seal in accordance with the present invention is used, for example, as a water pump seal for a vehicle such as a motor vehicle or the like, or is used as the other general purpose water pump seal.
2. Description of the Conventional Art
Conventionally, as shown in FIG. 4, there has been known a lip type seal 74 which is installed to an inner periphery of a shaft hole 72 of a housing 71 and slidably comes into close contact with a peripheral surface of a shaft 73 inserted to the shaft hole 72, and the lip type seal 74 has a first seal lip 75 which is arranged at a sealed fluid side A and is made of a rubber-like elastic material, and a second seal lip 76 which is arranged at an atmospheric air side B and made of a resin (refer to patent document 1).
Since the conventional lip type seal 74 mentioned above has a plurality of seal lips 75 and 76 each of which performs a seal operation, an excellent seal effect can be achieved, however, causes a disadvantage in the following point.
In particular, on the basis of necessity for recycle against an environmental problem in recent years, it is required to dispose of each of constructing parts of the lip type seal after being sorted by material, however, in the lip type seal 74 mentioned above, the first seal lip 75 made of the rubber-like elastic material is vulcanization bonded to a reinforcing ring 77 made of a metal, and both the elements 75 and 77 are formed as an integral vulcanization molded product. Accordingly, it is impossible to easily separate and sort both the elements 75 and 77 at a time of disposal, and it is therefore impossible to comply with the necessity for recycle mentioned above.
Accordingly, the applicant of the present invention has proposed a lip type seal 81 having a first lip seal member 82 provided with a first seal lip 83 arranged at a sealed fluid side A and made of a rubber-like elastic material, a second lip seal member 84 provided with a second seal lip 85 arranged at an atmospheric air side B and made of a resin, and two retaining rings 86 and 87 pinching both the lip seal members 82 and 84 from both sides in an axial direction and made of a metal, and having a structure in which these four parts are assembled without being bonded, as shown in FIG. 5 (refer to patent document 2). In accordance with this prior art, since each of the parts is not bonded, it is possible to easily separate and sort each of the parts. Accordingly, it is possible to comply with the necessity for recycle mentioned above. However, in the prior art, there is room of improvement in the following points.
(1) Assembly Retaining Characteristic Among Constructing Parts
In the lip type seal 81 mentioned above, two retaining rings 86 and 87 are respectively structured such as to have annular flat surface portions 86a and 87a for pinching both the lip seal members 82 and 84 from both sides in an axial direction and tubular portions 86b and 87b integrally formed with the flat surface portions 86a and 87a. The tubular portion 86b in the retaining ring 86 at the sealed fluid side A is fitted to an inner peripheral side of a cylinder portion 82a of the first lip seal member 82 and the tubular portion 87b in the retaining ring 87 at the atmospheric air side B is pressure inserted and fixed to an insertion hole 82b provided in the cylinder portion 82a of the first lip seal member 82. Accordingly, each of the parts is retained in an assembled state on the basis of setting of a fitting margin and a pressure inserting margin for the fitting and pressure insertion. However, in the case that each of the parts is exposed to force in the axial direction, an engagement structure for preventing separation in an axial direction of the parts is not particularly provided among the parts. Therefore, if the retaining ring 86 at the sealed fluid side A is pulled in an axial direction (a direction of an arrow C) so as to detach the lip type seal 81 in a state of being installed to an inner periphery of the shaft hole 72 of the housing 71, there is a case that only this retaining ring 86 is pulled out and the other parts remain in an installed state (alternatively, there may be a case that only the retaining ring 86 and the first lip seal member 82 are pulled out, and the second lip seal member 84 and the retaining ring 87 at the atmospheric air side B remain). This is because of nothing but the assembly retaining force among the parts depending only upon friction force.
(2) Installing Workability
Further, in the lip type seal 81 mentioned above, two retaining rings 86 and 87 do not particularly have any structure for defining an interval in an axial direction therebetween. Further, the first lip seal member 82 made of the rubber-like elastic material and pinched between both the elements can achieve a sufficient seal operation only when used in a state of being compressed in the axial direction. In other words, there is a risk that a leak of sealed fluid is caused between the first lip seal member 82 and the second lip seal member 84 made of the resin or the retaining ring 87 at the atmospheric air side B. Accordingly, at a time of installing the lip type seal 81 mentioned above, the lip type seal 81 is installed by using a snap ring 89 while the lip type seal 81 is brought into contact with a step portion 88 provided on an inner periphery of the shaft hole 72 of the housing 71 so as to apply a compression load in the axial direction, whereby the lip type seal 81 is installed in a state that the whole thereof is compressed in the axial direction between the step portion 88 and the snap ring 89. However, there is such a disadvantage that a work of installing by using the snap ring 89 while applying the compression load in the axial direction as mentioned above is extremely complicated.
Further, since the cylinder portion 82a of the first lip seal member 82 is provided with the annular insertion hole 82b which is open to the atmospheric air side B, a portion at an outer peripheral side from the insertion hole 82b in the cylinder portion 82a is formed to have such a shape that the atmospheric air side end portion 82c thereof terminates in a cylindrical shape. Accordingly, since the atmospheric air side end portion 82c rubs the inner peripheral surface of the shaft hole 72 at a time of the first lip seal member 82 being inserted into the inner periphery of the shaft hold 72 of the housing 71, there is a case that an evagination is caused in the atmospheric air side end portion 82c. 